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## Main Question or Discussion Point

Hello,

First of all, it is not a homework question, just something I wonder about.

The dominating electron-positron annihilation process at low energies is photon pair creation. What is the angular dependence of the total cross section?

For some reason I expect the head-on collision to have the highest cross-section and the collinear situation to have the lowest cross-section, is it really the case?

I am not a particle physicist, but I expect the calculation to be pretty difficult, involving IR divergences and collinear divergences. Could you give me a reference to the solution of the problem or the experimental results and perhaps give some physical intuition on the whole thing.

Thanks in advance.

First of all, it is not a homework question, just something I wonder about.

The dominating electron-positron annihilation process at low energies is photon pair creation. What is the angular dependence of the total cross section?

For some reason I expect the head-on collision to have the highest cross-section and the collinear situation to have the lowest cross-section, is it really the case?

I am not a particle physicist, but I expect the calculation to be pretty difficult, involving IR divergences and collinear divergences. Could you give me a reference to the solution of the problem or the experimental results and perhaps give some physical intuition on the whole thing.

Thanks in advance.